/Engine/Source/Editor/SceneOutliner/Public/SceneOutlinerGutter.h
If a visibility drag drop operation has entered this widget, set its item to the new visibility state
virtual void OnDragEnter ( const [FGeometry](API\Runtime\SlateCore\Layout\FGeometry) & MyGeometry, const [FDragDropEvent](API\Runtime\SlateCore\Input\FDragDropEvent) & DragDropEvent )